An electronic device can include an optical sensing system for quantifying surface or subsurface characteristics of an object onto which the electronic device is placed. The optical sensing system can include a light emitter to illuminate the object with light that may be absorbed or reflected by the object in a manner related to the characteristics of the surface or subsurface thereof. The optical sensing system may also include a light detector to generate electrical signals corresponding to light reflected from the object as a result of the illumination. These signals can be conveyed to the electronic device by the optical sensing system so that the electronic device can quantify characteristics of the surface or subsurface of the object.
In many cases, the electronic device may be undesirably responsive to noise (e.g., resulting from ambient light) present in the signals conveyed to it by an optical sensing system.